In many of the world's major cities atmospheric thermal inversions frequently trap air pollutants near ground level, resulting in poor ground-level air quality. There are no known practical means to address this immediate problem and alleviate poor air quality due to atmospheric inversions in large cities. (Long term measures include improved emission controls on automotive and industrial sources of pollutants).
As severe air pollution incidents in the affected cities become more frequent, industrial and transportation activities are curtailed and schools close for the duration of the emergency. A variety of impractical and very costly measures are currently being proposed to alleviate ground level pollution without any assurance of their effectiveness. For example, Mexico City is considering two huge cuts in the mountains that border the city for the polluted air to escape through. Another proposed scheme calls for the installation of several giant fans, spaced at intervals over a considerable distance, to move the polluted ground level air away from the city. Both these impractical schemes underscore the general principle that large expense of energy will be required to disperse polluted urban air trapped by inversions, either expended once--to modify the terrain, or over time, through the use of fans.
Around the turn of the century and through the nineteen-twenties power plants were located inside city boundaries in order to reduce transmission losses, and also so that the waste heat from the condensing steam could be used in local downtown `district heating` networks, prevalent at the time. Such use of the waste heat greatly improved overall fuel utilization by these early, inefficient power plants. Later on, power plants became associated with noise, unsightliness and pollution and were sited away from cities. Power plants can now be built with much improved environmental performance than in the past, making them acceptable for siting in cities always in need of power, particularly if they can also contribute to improved air quality.
It has been known that plumes of combustion gases emanating from tall stacks serving large power plants will penetrate inversions (Spurr, in "Journal of Meteorology", Volume 16; February 1959), and that large cooling tower plumes could also penetrate inversions (Brown and Sneck, in "Combustion"; November 1974). This information was primarily used to absolve power plant combustion gases from charges that they were contributing to ground level air quality problems during periods of inversion, and absolve cooling tower plumes from causing fogging, icing and poor visibility. The use of these plumes to break-up inversions has not been contemplated and claims that the plumes could be used to improve ground level air quality have not been made. U.S. Pat. No. 3,489,072 considers the use of a light weight, collapsible, tall and buoyant waste-gas discharge stack, variously supported and deployed, only for the purpose of obtaining at low cost increased dilution and dispersion of the discharged gas.